I have a 98.5 24v cummins auto trans, stock, no tuner ect. I have been noticing a bucking/surging when accelerating. It first started a few months back when under load. It seems to surg/ buck only around 1st/2nd gear. No codes have showed up during scan. The truck does seem to be lacking power. It is also shifting late when you put the pedal down as well (2600rpm) or so.

Here is the last couple months. I have driven it maybe 100km (60 miles) because I've had it in the shop while over been working. Brought it to a diesel shop in town, he was getting a low fuel pressure reading under load. Put a FASS system in it. Problem was still their. From his test drive he pointed out the late shift points and lack of power. He also noted that my charging syste/ batteries were weak.

I then took it to another shop to get another opinion: I put new alternator in, put 2 new 27 series batteries in, still wasn't getting the charge and ample voltage. After checking all my grounds and cleaning them, as well as new terminal clamps, it's charging great and I'm getting a good voltage reading. Truck is still bucking at this point.

Had it into a tranny shop. They took it for a week or so, did all their tests, adjusted bands, and said it all looks good to spec, and basically said it must be something engine related because my tranny is in good shape. I was shocked to hear this and actually expected a 3000$ bill and a new tranny.

So now I am stumped. What is causing this.

When accelerating in 1st gear it seems to hesitate a bit dropping into second. Once it is in second I give it some pedal and about 1800-2000 I feel a surge and buck that lasts until the next shift or taking foot off pedal slightly. It will surge 100-150 rpm. I also wanted to see what it does putting it in first gear. It is all normal and I can't get it to do it. Put it into second and accelerate, same problem. One final thing however, if I put it into second and let it move at idle speed. The bucking can be felt almost with every turn of the wheel. It doesn't feel like a surg at this point, just bucking.

There seems to be lack of power and hesitation while accelerating. Truck has 390,000km on it, I believe it was an engine swap. Doesn't blow any black smoke ever. Can somebody help me. These shop bills are piling up and I'm not getting anywhere in the right direction.

 

Hows your fuel filters? did you do the fass pump with filters or just a pump?

 

installed with fillers and by-pass the old fuel pump. i havent checked or touched the fass fuel filters. im assuming for less than 60 miles on the system that i should be good. im really leaning towards a tranny issue despite already having it in the tranny shop, and them telling me i didnt have any issues. my plan is to drop the truck off at the tranny shop monday morning for the week and hopefully they figure out this 2nd geer shutter. has anybody had anything similar to this?

 

What does your boost gauge do during this surge/bucking?

 

i actually do not have a boost guage on the truck. fuel pressure , boost, tranny temp guage cluster is on the install list for the winter months. I guess i was ruling out fuel and air issues after the one diesel shop did all of his tests under load and such.

 

What concerns me is the lack of power. It sure is a great tool to have boost, EGT and FP readings to correlate to the problem.

 

Test for AC noise form the alternator.